Chevrolet 10 Series 1970 Service Manual page 194

REAR SUSPENSION AND DRIVE LINE 4-18
A thrust pad mounted on the end of an adjusting screw
threaded into the c a r r ie r housing on all axles except the
13,500, lim its d eflection o f the rin g gear under high
torque conditions.
Involute splines a re incorporated in the axle shaft
flange and in the wheel hubs o f the 11,000 through 15,000
lb. axles. T h is design p rovid es fo r the d rivin g torque to
LUBRICANT
The lubricant le v e l should be p e rio d ic a lly checked and
maintained at le v e l o f f i lle r plug with a w arm axle. See
the lu brication section
recom m endations.
Lubricant Leaks
Lubricant leaks should be checked fo r at the pinion
flange o il seal, sealin g area o f joint between d ifferen tia l
c a r r ie r and axle housing, lubricant f ille r plug, housing
bowl cover, and at axle
these leaks consists o f rep lacin g the d e fe c tiv e seals or
gaskets involved as d escrib ed in this section.
U-BOLTS A N D HUB NUTS
A x le housing to r e a r
hub nuts should be p e rio d ic a lly inspected fo r
installation.
REAR AXLE NOISE D IA G N O SIS
Mechanical fa ilu re s o f the re a r axle are
sim ple to locate and c o r r e c t. N oise in a re a r axle is a
little m ore d ifficu lt to diagnose and re p a ir. One o f the
m ost essential p arts o f r e a r axle s e rv ic e
diagnosis.
One o f the cardinal points o f axle noise diagnosis is the
fa ct that a ll re a r a xles a re noisy to a certain d eg ree. The
action o f transm itting the high engine torque through a
90° turn reducing p ro p e lle r shaft speed produces noise in
r e a r axles. T h is point establishes the need fo r a line
between norm al and abnorm al
noises.
Slight axle noise heard only at a certain speed o r under
rem o te conditions must
noise tends to " p e a k " at varyin g speeds and the noise is
in no way indicative o f trouble in the axle.
If noise is presen t in an objectionable fo rm , loud or at
a ll speeds, an e ffo rt should be made to isola te the noise
as being in one p articu lar unit o f the veh icle. A x le noise
is often confused with other noises such as tire noise,
tran sm ission noise, p r o p e lle r
v e r s a l joint noise. Isolation o f the noise as in any one
unit req u ire s skill and exp erien ce. An attempt to e lim i­
nate a slight noise may b a ffle even the best o f diagnosti­
cians. Such p ra c tice s as ra isin g tir e p ressu re to e lim i­
nate tir e noise, listen ing fo r the noise at va ry in g speeds
MAINTENANCE AND ADJUSTMENTS
o f this manual fo r lubricant
shaft bearin gs. C orrectio n of
spring b olts and wheel
secure
re la tiv e ly
is proper
or unacceptable
be considered norm al.
shaft vib ration and uni­
be transm itted from the axle shaft to the hub through the
m ating splines.
The 15,000 and 17,000 lb. a xles have a rem ovable in ­
spection cover;
porate this feature, the c o v er is an in tegra l part o f the
axle housing.
and on d rive, float and coast, and under p rop er highway
conditions, turning the steerin g wheel from le ft to right
to detect wheel bearing noise, w ill aid even the beginner
in detecting a lleged axle noises. A x le noises fa ll into two
ca te go ries: g ea r noise and bearing noise.
G ear Noise
Abnorm al gea r noise can be recogn ized since it p ro ­
duces a cyclin g
nounced in the speed range at which it occurs, appearing
under either " d r i v e , "
G ear noise tends to peak in a narrow speed range or
ranges, while bearing noise w ill tend to rem ain constant
in pitch. Abnorm al gea r noise is ra re and usually o r ig i­
nates fro m the scorin g o f the ring gea r and pinion teeth
as a result o f insu fficient or im proper lubricant in new
assem b lies. Side g ea rs ra re ly g ive trouble as they are
used only when the re a r w heels tra vel at d ifferen t speeds.
Bearing Noise
D efective bearing w ill alw ays produce a rough grow l
that is constant in pitch and usually m ost noticeable under
" d r i v e " conditions. This fact w ill allow you to distinguish
between bearing noise and gea r noise.
1. Pinion bearing noise resu lting fro m a bearin g failu re
can be identified by a constant rough sound. Pinion
bearings a re rotating at a higher speed than d iffe re n ­
tia l side bearings o r axle shaft bea rin gs. T h is p a r­
ticu lar noise can be picked up best by testing the car
on a smooth road (black top). H ow ever, care should
be taken not to confuse tir e noise with bearing or
gea r noise. If any doubt exists, tir e treads should be
axle
examined fo r irr e g u la ritie s that would produce such
noise.
A xle 2. Wheel bearing noise may be confused with re a r axle
noise. T o differen tia te between wheel bearin gs and
re a r axle, d rive the veh icle on a smooth road at
m edium -low speed. With tra ffic perm ittin g, turn the
veh icle sharply right and left. If noise is caused by
wheel bearings, it w ill in crease in the turns because
o f the side loading.
front or re a r wheel bearings, inspection w ill be
necessary.
3. Side bearings w ill produce a constant rough noise o f
a slo w er nature than pinion bearin gs.
noise w ill not fluctuate in the above wheel bearing
test.
11,000 and 13,500 lb. a xles do not in c o r­
pitch (whine) and w ill be v e ry p ro ­
" f l o a t " o r " c o a s t "
If noise cannot be isolated to
CHEVROLET TRUCK SERVICE MANUAL
conditions.
Side bearing